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The Sky This Week, 2011 January 25 - February 1

A starry chase through the seasons
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Jupiter and Io, 2011 JAN 23, 23:30 UT 


The Moon wanes in the early morning sky this week. The Last Quarter phase occurs on the 26th at 7:57 am Eastern Standard Time. Luna spends the week coursing along the southern reaches of the Ecliptic, passing through the rising constellations of the early summer sky. Look for the Moon on either side of the ruddy star Antares low in the southeast in the pre-dawn sky on the 28th and 29th. The next morning her slimming crescent may be found about five degrees south of dazzling Venus.

After the chilly nights and mornings we’ve been experiencing lately our view of the pre-dawn sky is a reassurance of the inevitable arrival of summer. The ever-moving cycle of the seasons is played out each year in the sky, and this is one of the best times of the year to experience it. The players involve two of the most distinctive constellations in the sky, and in particular their brightest stars. Right now skywatchers in the mid-evening hours can easily spot the brighter stars of Orion, the Hunter, straddling the meridian. It’s quite easy to trace out the majestic striding figure of a man, knees and shoulders marked by bright stars, with three stars forming an obvious "belt". The upper left star has an unusually reddish tinge, especially compared to its compatriots. The ruddy star is Betelgeuse, a very evolved star near the end of its luminous life. Its girth is so large that if it were placed in the Sun’s position in the solar system the inner planets out to Mars would be inside its tenuous outer layers. If you follow the progress of Betelgeuse through the rest of the night you’ll find that as it sets in the west a similar ruddy star is rising in the southeast. This star is Antares, lead star of Scorpius, the Scorpion. In mythology the lowly scorpion was sent by the gods to punish the mortal Hunter for his desires toward the goddess Diana. The scorpion killed the boastful Orion, who was raised to the sky by the heartbroken goddess. The scorpion was also offered a place in the sky, but opposite that of Orion. The two rivals are now in a perpetual chase through the seasons, with their distinctive red stars serving as seasonal markers for winter and summer. So if you find yourself up before the Sun this week, look to the southeast for Antares and know that the chill of late January will soon be replaced by the balm of late June evenings.

Well before Orion reaches his pinnacle in the current night sky the eye is still drawn to the bright light of giant Jupiter. The planet is now well past the meridian as twilight deepens, and he sets at around 9:30 pm. It’s becoming harder to catch a good glimpse of Old Jove through the telescope against a dark sky and steady air. Your best views will be in the early evening between 6:00 and 7:30 pm. If conditions are good, however, there is still much to see on the planet’s distant cloud tops, so keep an eye on him as long as you can.

Saturn now rises in the eastern sky at around 11:00 pm and is well-placed for viewing throughout the early morning hours. Your best plan right now is to either stay up late and catch him at around 2:00 am or get up at around 5:00 am to catch him before the onset of twilight. His rings are now tipped about 10 degrees to our line of sight, and the giant white storm that has appeared in his northern hemisphere shows no signs of abating. He will be well worth watching in the weeks and months to come!

Venus graces the southeastern sky in the pre-dawn morning twilight hours. She passed by ruddy Antares last week; this week finds her passing above the stars of the Sagittarius "teapot". Look for her in the company of the Moon before dawn on the morning of the 30th.

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